[1.11.x] Fixed #28389 -- Fixed pickling of LazyObject on Python 2 when wrapped object doesn't have __reduce__().

Partial revert of 35355a4ffe.

django/utils/functional.py

@@ -300,13 +300,14 @@ class LazyObject(object):
             self._setup()
         return (unpickle_lazyobject, (self._wrapped,))
 
+    # Overriding __class__ stops __reduce__ from being called on Python 2.
+    # So, define __getstate__ in a way that cooperates with the way that
+    # pickle interprets this class. This fails when the wrapped class is a
+    # builtin, but it's better than nothing.
     def __getstate__(self):
-        """
+        if self._wrapped is empty:
-        Prevent older versions of pickle from trying to pickle the __dict__
+            self._setup()
-        (which in the case of a SimpleLazyObject may contain a lambda). The
+        return self._wrapped.__dict__
-        value will be ignored by __reduce__() and the custom unpickler.
-        """
-        return {}
 
     def __copy__(self):
         if self._wrapped is empty:

docs/releases/1.11.4.txt

@@ -15,3 +15,6 @@ Bugfixes
 
 * Fixed ``QuerySet.union()`` and ``difference()`` when combining with
   a queryset raising ``EmptyResultSet`` (:ticket:`28378`).
+
+* Fixed a regression in pickling of ``LazyObject`` on Python 2 when the wrapped
+  object doesn't have ``__reduce__()`` (:ticket:`28389`).

tests/utils_tests/test_lazyobject.py

@@ -187,11 +187,13 @@ class LazyObjectTestCase(TestCase):
     def test_pickle(self):
         # See ticket #16563
         obj = self.lazy_wrap(Foo())
+        obj.bar = 'baz'
         pickled = pickle.dumps(obj)
         unpickled = pickle.loads(pickled)
         self.assertIsInstance(unpickled, Foo)
         self.assertEqual(unpickled, obj)
         self.assertEqual(unpickled.foo, obj.foo)
+        self.assertEqual(unpickled.bar, obj.bar)
 
     # Test copying lazy objects wrapping both builtin types and user-defined
     # classes since a lot of the relevant code does __dict__ manipulation and